Scientific Forecaster Discussion
fxus61 krlx 081244
Area forecast discussion
National Weather Service Charleston WV
744 am EST sun Dec 8 2019
high pressure exits today/tonight. Rain develops early Monday
with a strong cold front Tuesday. Sharply cold air and snow
showers for Wednesday. Break until the weekend, then unsettled.
Near term /through tonight/...
as of 740 am Sunday...
Increased sky grids considerably this morning along the
southeast slopes, including much of Pocahontas co. This should
gradually erode under the increasing cirrus today. Elsewhere,
sky grids were bumped up quite a bit this morning to account
for a pinch of moisture around 850 mb which has resulted in an
expanding cloud deck across southeast OH, northeast Kentucky and
central WV. Model soundings bear this out and keep this cloud
deck in place along and especially north of the Ohio River today
while migrating the deck into northern WV over the next couple
As of 625 am Sunday...
Increased the winds slightly over The Lowlands and made some
sky grid adjustments as well.
As of 225 am Sunday...
High pressure departs to the east while low pressure gets
organized in the Lee of The Rockies. Strong baroclinic zone will
develop with the flow aloft turning southwesterly later today
into tonight. Counterclockwise flow will bring milder conditions
ahead of the frontal system with the main surface low staying to
the west of the County Warning Area while it moves southwest to northeast.
Expecting a moisture surge from the deep south that will get
caught up ion the aforementioned southwesterly flow in the lower
levels. Multiple disturbances in the flow aloft will trigger
showers mainly after 00z Monday, leading to wider coverage by
12z Monday morning. The nature of the surface low tracking
towards Quebec and a significant lag in a trough aloft to push
the system out results in what will be a longer event,
stretching into the short term time frame.
Southerly flow brings a warming trend for the near term well
ahead of the cold front. Expecting winds to be on the gradual
increase with a strengthening pressure gradient and stronger
Short term /Monday through Wednesday/...
as of 230 am Sunday...
This period begins with rain spread across the region associated
with a southern stream low pressure system prog to advect a
warm frontal boundary into the area as the track of the low
moves north just west of the area. An abundant moisture
transport will take place from the Gulf and with the moisture
vectors coinciding with the upper level flow this will provide
precipitable water values of 2 Standard deviations above climatological norm
to traverse overhead for a prolonged period of time. With a
southwest to northeast track over the area, a low level jet of
60kt and precipitable water values of 1.25 inches (at the climate max)
persisting through Tuesday we can expect light to moderate and
at times, heavy showers. Due to the lows parent trough and
surface front ingesting a short wave disturbance (moving into
the Gulf from the west) moisture supply will increase and rainfall
amounts will be even be more enhanced into Wednesday making
total qpfs from 1.25 to 2.25 inches, with the most in the
northeastern parts of the County Warning Area. By Tuesday night, a wintry mix is
feasible for the mountain terrains and the Ohio Valley as cold
air advects in during fropa dropping 850mb temps down to -10c by
the early morning. Snow shower chances will make its way across
areawide later Wednesday morning. Show shower chances will
continue into the afternoon when finally the feature will have
moved out of the area.
Anticipating how much rainfall is capable of dropping over this
lengthy time frame raises concerns for potential flooding. A
watch may need to be issued in later shifts. Wpc has already
issued a marginal threat for excessive rainfall for Monday
morning into Tuesday morning.
Long term /Wednesday night through Saturday/...
as of 300 am Sunday...
The good news is that the precipitation will have ended to
start this period and the aforementioned cold front will be
long past the area although making US very cold in its wake
ending the short short warming trend from the previous few days.
Even though models diverge there is a slim chane for wrap
around snow showers due to a possible wave developing on the
backside of the front which will mostly just affect the
mountains through Wednesday if it even materializes. High
pressure will build in fast and most likely cut chances of
precipitation off at that point anyways. Temperatures will fall
drastically below seasonable for Wednesday and Thursday with
cold Canadian air advecting in causing Wednesday nights forecast
to be almost 15c below norm. However, these temps will level
out to normal starting Friday and continue through the weekend.
High pressure will maintain briefly into the beginning of the
weekend when models hint of the next system to affect the area
developing to the south. It is forecast to approach on the
eastern side of the mountains which would imply a northern
stream starting off as snow an then transitioning to all rain as
it moves north. However, models do diverge significantly at
this point and we cannot put too much weight on them. The take
away here is that next weekend is becoming more likely to be
Aviation /13z Sunday through Thursday/...
as of 630 am Sunday...
Wind gusts out of the S to south-southeast today at 15-25kts generally
Ceilings lower ahead of the next approaching frontal system.
Clouds increase through 21z today. Showers move in after 05z
tonight. As the lower levels of the atmosphere saturate where
showers become more persistent, MVFR ceilings should enter the
fold for some of the terminals after 09z Monday. Also have the
potential for MVFR visibilities during the same time frame in
Forecast confidence and alternate scenarios through 12z Monday...
Forecast confidence: high.
Alternate scenarios: none.
Experimental table of flight category objectively shows consistency
of weather forecast office forecast to available model information:
h = high: taf consistent with all models or all but one model.
M = medium: taf has varying level of consistency with models.
L = low: taf inconsistent with all models or all but one model.
UTC 1hrly 12 13 14 15 16 17 18 19 20 21 22 23
EST 1hrly 07 08 09 10 11 12 13 14 15 16 17 18
crw consistency h h h h h h h h h h h h
heights consistency h h h h h h h h h h h h
bkw consistency h h h h h h h h h h h h
ekn consistency h h h h h h h h h h h h
pkb consistency h h h h h h h h h h h h
ckb consistency h h h h h h h h h h h h
After 12z Monday...
IFR expected Monday/Tuesday in rain. IFR possible Tuesday night
and Wednesday in snow showers, most likely in the mountains.